Butterflies deposit eggs — singly or in clusters — in spring, summer or fall, depending on the species. A good nectar source promotes the production of large numbers of eggs. Some lay eggs on only one or a few plant species, others on many kinds, usually on those appropriate as larval food. Eggs usually hatch within a few days. Nine out of 10 eggs never become adults because predators, mainly birds, think the eggs, caterpillars and butterflies are delicious.

Emerging caterpillars feed first on their eggshells, then the host plant. They shed their “skin” usually four or five times, growing larger with each stage (called an “instar”). Caterpillars with abundant, high-quality food mature earlier than poorly fed larvae.

A tussock moth pupating on the underside of a leaf.2

The full-sized caterpillar spends about a day forming a green or brown pupa (chrysalis) using silk produced by its glands. The chrysalis has a smooth, hard surface and is suspended by a thin fiber from a stem or twig. Some butterflies, such as skippers, pupate inside a thin covering of silk and leaves. Moths spin a “cocoon,” usually in a shell surrounded by a protective fuzzy, cottony covering.

Depending on the species and temperature, the chrysalis stage usually lasts about two weeks. During this time, they astonishingly develop into an adult. Some species go through a hibernation stage called a diapause, before the pupa splits and the butterfly emerges. During the first few hours, the butterfly’s wings expand, the skin hardens and then it is able to fly, sip nectar, mate and lay eggs, thus repeating the life cycle.

From egg-to-caterpillar-to-butterfly takes about five to six weeks. Some species have only one generation per year. Others may go through two or three generations in a season. Most live only two or three weeks, although some, such as the mourning cloak, which spends the winter as an adult, may live for 10 months or more.

Source: University of Minnesota, James Ford Bell Museum of Natural History.

Attracting Butterflies to Your Garden

An adult zebra swallowtail.1

Monarch being handled.2

Select a variety of nectar-producing plants in flower throughout the season, especially those that bloom in mid to late summer, when most butterflies are active. Flowers with multiple florets that produce abundant nectar are ideal. (Double flowers are bred for appearance, not nectar production.) Adults will lay their eggs on specific plants that will serve as a food source for the caterpillars that hatch.

Provide shelter. Butterflies prefer to feed and lay eggs away from gusty winds. A row of shrubs or trees provides a windbreak. Plant tall plants at the back and sides of the garden for additional protection.

Wet sand or a mud puddle nearby encourages “puddling.” Though they get their sugar from plant nectar, butterflies need other nourishment for reproduction. For that, they sip from mud puddles, ingesting salts and minerals from the soil. Puddling is mostly seen in males. They incorporate those nutrients into their sperm, which when mating, are transferred to the female. These extra salts and minerals improve the viability of the female’s eggs, increasing the couple’s chances of passing on their genes to another generation.

Avoid using broad-spectrum pesticides. Although caterpillars will chomp on some plants, they need this to metamorphose. Eventually your garden will attract natural predators for other pests attacking your garden.

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